In a typical power distribution network, substations deliver electrical power to consumers via interconnection cables and electrical apparatuses, e.g., transformers, switches, circuit breakers, fuses, etc. The cables terminate on bushings passing through walls of metal encased equipment, such as capacitors, transformers, switchgear, etc. Increasingly, this equipment is “dead front,” meaning that the equipment is configured such that an operator cannot make contact with any live electrical parts. Dead front systems have proven to be safer than “live front” systems, with comparable reliability and low failure rates.
Various safety codes and operating procedures for underground power systems require a visible disconnect between each cable and electrical apparatus to safely perform routine maintenance work, such as line energization checks, grounding, fault location, and hi-pot testing. One approach to meeting this requirement for a dead front electrical apparatus is to provide a “separable connector system” including a first connector assembly connected to the apparatus and a second connector assembly connected to an electric cable. The second connector assembly is selectively positionable with respect to the first connector assembly. An operator can engage and disengage the connector assemblies to achieve electrical connection or disconnection between the apparatus and the cable.
Generally, one of the connector assemblies includes a female style connector, and the other one of the connector assemblies includes a corresponding, male style connector. During a typical operation for making an electrical connection, an operator slides a female style connector over its corresponding male style connector. In some cases, each of the connector assemblies can include two connectors. For example, one of the connector assemblies can include ganged, substantially parallel female style connectors, and the other of the connector assemblies can include substantially parallel male style connectors that correspond to and are aligned with the female style connectors.
In general, two basic types of separable connector systems have conventionally been provided, namely, deadbreak connector systems and loadbreak connector systems. Deadbreak connector systems require connection or disconnection of cables while the equipment and the cables are de-energized. That is, deadbreak connectors are mated and separated only when there is no voltage present at and load current flowing through the connectors. A bolted connection is made such that the cable connector is screwed into the bushing with a coupling bolt in, e.g., a T-body 600 A deadbreak elbow. Deadbreak connector systems for high voltage equipment are typically rated for currents of 600 amperes.
To avoid power interruptions required by deadbreak connector systems, loadbreak connector systems have been developed that allow connection and disconnection to equipment when operating voltage and load current are present. This is done with a special arc interrupting probe tip in the loadbreak elbow. Loadbreak connector systems, however, are typically rated for much lower currents (typically about 200 amperes) than deadbreak connector systems.
The loadbreak elbow connector comprises an insulated portion having a recessed inner conical opening, a threaded lug, and a loadbreak probe with an arc follower tip portion. The loadbreak probe is screwed into the threaded lug coaxially within the inner conical opening. The loadbreak probe is made from a conductive material that contacts corresponding finger contacts into a mating loadbreak bushing connector to complete a circuit that includes the loadbreak elbow and the mating loadbreak connector. When mated together, an end of the male type conically shaped bushing connector is disposed substantially within the recessed inner conical opening of the loadbreak elbow. In this recessed inner conical opening, the loadbreak elbow includes a locking ring that is molded into the body of the loadbreak elbow connector that keeps the loadbreak elbow mechanically coterminous with the mating loadbreak male type bushing connector (e.g., loadbreak bushing). To connect and disconnect the loadbreak connectors, a person can manipulate the arrestor elbow onto and off of the male connector (e.g., loadbreak bushing) by using a liveline tool or “hot stick” in an operating eye of the loadbreak elbow to push on or pull off the loadbreak elbow with the loadbreak bushing The different mechanical and electrical mating interfaces of the 600 A deadbreak and 200 A loadbreak connectors are not compatible with one another, however, both use similar insulated mechanical conical portions of the male bushing and female elbow.
Transformers used in wind farm applications are generally equipped with 600 A deadbreak bushings. To obtain over voltage protection for the system, elbows having lightning or surge arrestors built-in (“arrestor elbows”) are attached to the transformer bushings. Traditionally, companies have only offered arrestors in 200 A loadbreak elbows, which, as set forth above, cannot be directly coupled to the 600 A deadbreak bushings. To compensate for this, companies have coupled intermediary connector adapters, such as an extender in combination with a loadbreak reducing tap plug (LRTP), between the standard 600 A deadbreak bushings and the 200 A arrestor loadbreak elbows. This approach is not desirable at least because the extra pieces required increase the cost of the installation and increase deadfront spacing requirements for this type of 600 A bushing—LRTP adapter-200 A arrestor elbow configuration.